On Feb. 18, 1987, the Environmental Protection Agency (EPA) published in the Federal Register, Volume 52, No. 32, 40 CFR Part 60 entitled "Standards of Performance for New Stationary Sources, Standards of Performance for New Sources, Residential Wood Heaters." These regulations were proposed to control the burgeoning wood stove industry which many believed was substantially adding to the air pollution problem in the United States. The states of Oregon and Colorado had already passed requirements for wood burning devices to control the emission of particulate matter and potential carcinogens.
In the period when the proposed regulations were issued, so-called airtight stoves were very popular. These wood burning stoves consumed a small amount of wood over a long period of time and generated a steady source of heat. The slow combustion of the wood, however, resulted in a large amount of particulate matter being emitted from the chimney attached to the airtight wood burning heater. In an attempt to clean up the air in areas where wood burning residential heaters were in common usage, the Environmental Protection Agency proposed stringent requirements for wood burning stoves of the airtight variety. The Environmental Protection Agency proposed dates after which it would no longer be possible to use the then currently available airtight stove. The EPA recognized that conventional wood burning fireplaces were not in this same category or did not pollute as much as the airtight stoves in view of the high volume of air to fuel used and in view of the high burning rate and, in turn, the combustion temperature of a fireplace which would consume the particulate material In recognition of this, the EPA also proposed limits above which a wood heater did not have to be certified and would be exempt from the proposed regulations. The two proposed criteria were at least a 35:1 air to fuel ratio and a burn rate of at least 5 kg of wood per hour. If a wood burning heater operated at or above these limits, it was believed that it would produce a very small amount of particulate material and pollutants.
Since the above-quoted exemption criteria would require the wood burning stove to burn wood at a more rapid rate than an airtight stove, the EPA placed limits on the construction of wood burning residential heaters so that the user of the heater would not alter it to slow the combustion rate. For example, a heater could not have secondary air input which could be blocked off by the homeowner using aluminum tape or the like after the unit had been certified. Also, the normal non-precision fits between the cast iron parts making up the wood burning heater could not be caulked or sealed with aluminum tape after the unit had been certified. There was also a tendency on the part of the homeowner to remove the damper from the chimney of the fireplace so that it did not interfere with the small volume of smoke emitted by an airtight wood burning heater.
In order to become exempt from the EPA requirements, it was necessary for a wood burning residential heater to operate with the wood inlet door closed, and with the damper for the air inlet closed, as they would normally be produced by the factory without subsequent modification. Also, knowing the tendency of homeowners to remove the damper or other closure, the EPA made it a requirement that the heater have a damper permanently attached which could not be removed readily by a homeowner using household tools.
In view of the stringent requirements proposed by the EPA, many companies went out of the wood burning stove business Several of the larger companies produced catalytic secondary combustion chambers to reduce the amount of pollution which while effective substantially increased the cost of the stove. It was also possible, as noted above, to produce a wood burning heater which was exempt from the EPA requirements since it operated under conditions which substantially reduced the amount of particulate material and air pollutants being emitted from the wood burning heater.